Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are particularly suitable for an image pickup apparatus using a solid-state image pickup element, such as a video camera, an electronic still camera, a broadcasting camera, or a monitor camera.
Description of the Related Art
In photography, shaking causes a blur in a picked-up image. There are proposed various imaging optical systems having an image stabilization function for reducing the blur of a picked-up image.
In general, a mechanism for reducing the blur of a picked-up image by vibrating a part of lens units of the imaging optical system is required to have a large correction amount of the blur of a picked-up image and to have a small movement amount of a lens unit to be vibrated for correcting the blur of a picked-up image (image stabilizing lens unit). Further, the entire imaging optical system is required to be small in size. In addition, when the image stabilizing lens unit is decentered, if many decentering aberrations such as decentering coma, decentering astigmatism, decentering chromatic aberration, and decentering field curvature are generated, the image is blurred.
For instance, when many decentering distortions are generated, a movement amount of the picked-up image becomes different between on an optical axis and in a peripheral portion of a screen. For this reason, when the image stabilizing lens unit is decentered for correcting the blur of a picked-up image the optical axis, the same phenomenon as the blur of a picked-up image occurs in the peripheral portion of the screen, which causes conspicuous deterioration of optical characteristics.
As described above, it is required that deterioration of image quality is small when the image stabilizing lens unit is decentered. In addition, in order to downsize the entire apparatus, it is required that decentering sensitivity of the image stabilizing lens unit (a ratio ΔX/ΔH of a correction amount ΔX of image blur to a unit movement amount ΔH) is large. Further, it is required that the image stabilizing lens unit itself has a small size and a light weight.
Hitherto, there is known a telephoto type zoom lens in which some lens units are moved as an image stabilizing lens unit so as to have a component in a direction perpendicular to the optical axis so that an imaging positron is moved in the direction perpendicular to the optical axis for image stabilization.
U.S. Pat. No. 7,471,462 discloses performing the image stabilization by a second lens unit in a three-unit zoom lens including, in order from an object side to an image side, a first lens unit to a third lens unit respectively having positive, negative, and positive refractive powers, and in a four-unit zoom lens including, in order from the object side to the image side, a first lens unit to a fourth lens unit respectively having positive, negative, positive, and positive refractive powers. Japanese Patent Application Laid-Open No. 2000-047107 discloses performing the image stabilization by a second lens unit in a six-unit zoom lens including, in order from the object side to the image side, a first lens unit to a sixth lens unit respectively having positive, negative, positive, negative, positive, and negative refractive powers. Other than that, there is known a telephoto type zoom lens having a high zoom ratio using an inner focus type.
U.S. Pat. No. 8,049,968 discloses a zoom lens including, in order from the object side to the image side, a first lens unit to a fifth lens unit respectively having positive, negative, positive, positive, and negative refractive powers, in which the lens units are moved during zooming, and the fifth lens unit is used for focusing. U.S. Pat. No. 8,537,471 discloses a zoom lens including, in order from the object side to the image side, a first lens unit to a sixth lens unit respectively having positive, negative, positive, positive, negative, and positive refractive powers, in which the first, third, fourth, and fifth lens units are moved during zooming, and focusing is performed by a small-size and lightweight lens unit as a part of the fifth lens unit. In addition, U.S. Pat. No. 8,537,471 discloses performing the image stabilization by a part of the fifth lens unit.